Methyl isobutyl ketone (MIBK) is an important solvent in many chemical industries. MIBK is produced from acetone and hydrogen in a three-step process through diacetone alcohol (DAA) and mesityl oxide (MO) intermediates. MIBK is also manufactured from acetone and hydrogen in a one-step liquid phase process, which is commercially preferred over the three-step process since it offers lower capital investment and operating costs. It also avoids the low conversion of acetone in the first reactor as well as the reversion of mesityl oxide to acetone in the second reactor which are experienced in the three-stage process. The commercial one-step MIBK reactor is operated at liquid phase by contacting acetone and hydrogen at high pressure which ranges between 30-100 atm.
In the commercial MIBK one-step liquid phase process, hydrogen and acetone are passed over metal solid base catalysts at moderate temperatures and high pressure. MIBK is produced with other products and then recovered using four distillation columns wherein the first column removes light hydrocarbons and the second distillation column recycles unconverted acetone. A decanter is then located upstream of the last two columns and is used to separate an aqueous phase. The third column removes propanol-water mixture while the last column separates a purified MIBK as distillate and heavy products including diisobutyle ketone (DIBK) as bottoms stream. In other processes, three distillation columns are used for separating MIBK from other products in which acetone is separated in the first distillation column and recycled back to the reactor.
Although the commercial one-step liquid phase process has many advantages over the three-step process, it still has some disadvantages since the reactor is operated at high pressure with acetone conversion in the range of 35% to 40%. The high pressure process increases both the capital and operating costs of the plant. In addition, the low conversion of acetone increases the recycle-flows and thus equipment sizes of the plant.